Georgia
Rainwater
Harvesting
Guidelines
In accordance with Appendix I
!Rainwater Recycling Systems of the
2009 Georgia Amendments to the
2006 International Plumbing Code

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Georgia Rainwater Harvesting Guidelines
PREFACE
The Georgia Rainwater Harvesting Guidelines are intended to assist all parties involved in the design,
construction, inspection and maintenance of rainwater harvesting systems and to help successfully comply
with Appendix I-‘Rainwater Recycling Systems’ of the 2009 Georgia Amendments to the 2006 International
Plumbing Code (IPC). The parties mentioned above include owners, building officials, design professionals
and contractors. This consensus document is the product of the parties listed below:
Guideline Committee Members:
Frances Carpenter, chair Bill Guinade
Max Rietschier Marvin Richards
Bill Morris Tom Carty
Ernest U. Earn Bob Freeman
David Freedman Phillip T. McCreanor, Ph.D.
Randy Starr Eddie Van Giesen
Chris Kumnick Shawn Hatley
Ryan Meres Frank Henning
Greg Jeffers
The Guidelines Committee wishes to take this opportunity to express our sincere appreciation to those
individuals who donated their time and effort to the development and production of this document. Special
thanks goes out to Eddie Van Giesen and Frances Carpenter for their efforts as principal authors and editors
of this document.
Disclaimer and Notice:
While the information presented in these guidelines is believed to be correct, the parties involved assume no
responsibility for its accuracy or for the opinions expressed herein. The material presented in this publication
is not considered “Code” and should only be used for reference and guidance in complying with the
requirements of Appendix I ‘Rain Water Recycling Systems.’ All rainwater harvesting systems shall comply
with the Georgia State Minimum Standard Plumbing Code (2006 IPC with Georgia Amendments) and all
other applicable State Minimum Standard Codes for construction. Users of information from this publication
assume all liability arising from such use.
The 2009 Georgia Amendments to the International Plumbing Code which contain Appendix I ‘Rain Water
Recycling Systems’ can be downloaded from the Department of Community Affairs website at the following
link: http://www.dca.ga.gov/development/ConstructionCodes/programs/codeAmendments.asp
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TABLE OF CONTENTS
Figure 4-12 Corrugated steel tank................................................................................. 11
CHAPTER 1
.................................................................................................... 1
GENERAL INFORMATION
.............................................................................1
1.1 Purpose
................................................................................................... 1
1.2 ARCSA
.....................................................................................................1
CHAPTER 2
.................................................................................................... 3
INTRODUCTION TO RAINWATER HARVESTING
........................................ 3
2.1 The Big Picture
....................................................................................... 3
2.2 History
..................................................................................................... 5
.................................................................. 6
2.3 Current Usage of Rainwater
.............................................................................7
2.4 Response to Drought
................................................................................................. 10
2.5 Benefits
.................................................................. 10
2.6 Economics and Feasibility
........................................................................................ 11
2.7 In conclusion
.................................................................................................. 12
CHAPTER 3
SYSTEM SIZING AND WATER BALANCING
............................................. 12
3.1 Water Conservation
.............................................................................. 12
3.2 Stormwater Runoff Reduction
............................................................. 13
3.3 Green Building
...................................................................................... 14
3.4 System Sizing
........................................................................................ 15
3.5 How Much Water Can Be Captured?
................................................... 16
3.6 Calculating Storage Capacity
.............................................................. 18
3.7 Water Conservation Supplemental to Other Resources
.................. 20
3.8 Summary
............................................................................................... 20
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CHAPTER 4
.................................................................................................. 21
HARVESTING COMPONENTS
....................................................................21
4.1 Introduction and Fundamental Elements
........................................... 21
4.2 The Catchment Surface
........................................................................ 24
-Metal Roof
................................................................................................... 24
-Clay/Concrete and Tile Roof
..................................................................... 24
-Composite or Asphalt Shingle
.................................................................. 25
-Wood Shingle, Tar, and Gravel
................................................................. 25
............................................................................................................ 25
-Slate
......................................................................................... 25
-Vinyl/rubberized
..................................................................... 25
4.3 Gutters and Downspouts
................................................................... 26
-Gutter Sizing and Installation
.................................................................................. 26
4.4 Primary Filtration
...............................................................................................27
-Leaf Screens
......................................................................................27
-Downspout Filters
-Strainer Baskets
.........................................................................................27
-First-Flush Diverters
.................................................................................. 28
4.5 Storage
................................................................................................... 29
-Tank Siting
.................................................................................................. 29
4.6 Tank Materials
...................................................................................... 33
-Rain Barrel
.................................................................................................. 33
-Above Ground Polypropylene
.................................................................. 33
-Fiberglass
................................................................................................... 34
-Below Ground Polypropylene
................................................................... 34
-Metal
............................................................................................................ 36
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-Concrete
..................................................................................................... 36
-Wood
........................................................................................................... 37
4.7 Pumps and Controls
............................................................................ 37
4.8 Treatment and Disinfection
.................................................................. 39
CHAPTER 5
.................................................................................................. 40
WATER QUALITY AND TREATMENT COMPONENTS
.............................. 40
5.1 Introduction
........................................................................................... 40
5.2 Factors Affecting the Quality of Harvested Rainwater
...................... 40
.................42
5.3 Water Treatment For Non-potable Outdoor Use Systems
....................42
5.4 Water Treatment For Non-potable Indoor Use Systems
5.5 Additional Requirements for Use as Cooling Tower Make Up Water
6
4
......................................................................................... 46
5.6 Conclusions
.................................................................................................. 47
GLOSSARY
................................................................................................... 51
References
...................................................................................................... 52
Websites
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List of Figures
Figure 2.1 Statewide Water Level Restrictions................................................................. 4
Figure 2.2 Lake Lanier Level Diagram.............................................................................. 6
Figure 2.3 Aerial Photo of Lake Lanier 2007.................................................................... 7
Figure 2.4 ! Basic Hydrological Cycle.................................................................................8
Figure 2.5 The Hydro-Illogical Cycle................................................................................ 9
Figure 3.1 Catchment area of typical roofs...................................................................... 16
Figure 4.1 Diagram of above ground cistern................................................................... 21
Figure 4.2 Diagram of below ground cistern................................................................... 22
Figure 4.3 Rainwater Harvesting Flow Chart.................................................................... 23
Figure 4.7 Calming Inlet.................................................................................................. 26
Figure 4.5 Downspout filter............................................................................................. 27
Figure 4.6 Strainer Basket................................................................................................ 27
Figure 4.7 First Flush Diverter.......................................................................................... 28
Figure 4.8 Wooden tank.................................................................................................. 30
Figure 4.9 Schematic for 350 gallon Rain barrel........................................................ 32
Figure 4.10 75 gallon Rain barrel.................................................................................... 33
Figure 4.11 Plastic polypropylene tanks.......................................................................... 33
Figure 4.12 Below ground Fiberglass tanks..................................................................... 34
Figure 4.13 Below ground polypropylene tanks.............................................................. 35
Figure 4-14 Corrugated steel tank................................................................................... 36
Figure 4.15 Wooden aboveground tank.......................................................................... 37
Figure 4.16 Submersible on demand pump with floating suction .................................. 38
Figure 4.17 On demand external pump........................................................................... 38
Figure 5.1 First flush diverter............................................................................................ 41
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List of Tables
Table 3.1 Percentage of water uses................................................................................... 13
Table 3.2 Major GA Cities Annual Precipitation 1971-2000 - 30 year average (inches).... 17
Table 3.3 Table for rainwater potential collection from roof surfaces............................. 18
Table 4.1 Storage tank materials descriptions.................................................................. 31
Table 4.2 Tank volume for a given height and diameter (1,000 GAl units)....................... 32
Table 4.3 Typical minimum requirements of commons fixtures in water-harvesting........ 37
Table 5.1 Treatment Techniques...................................................................................... 45
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CHAPTER 1
GENERAL INFORMATION
1.1 Purpose
Rainwater, for purposes of this document, is Installers and the general public are advised to
water collected from roof surfaces during rain comply with local and state codes.
events. This water is then stored in tanks or On January 1, 2009, Appendix I ‘Rainwater
cisterns for later use. Potential uses include Recycling Systems’ of the Georgia 2009
indoor non-potable applications (toilet Amendments to the 2006 International
flushing) and outdoor non-potable applications Plumbing Code took effect allowing rainwater
(irrigation systems, hose bibs, etc). Rainwater harvesting in certain applications throughout
Harvesting (RWH) in its essence is the the state. The guidelines presented in this
collection, conveyance and storage of document (Georgia Rainwater Harvesting
rainwater. Rainwater collected from roofs is Guidelines) will assist regulators, rainwater
not “recycled water”, nor is it “gray water”. It systems designers and end users in rainwater
is fresh water that is in abundant supply, and is harvesting best management practices. The
generally undervalued in the United States. water available from such systems will offer
high quality water to supplement utility-
Rainwater Harvesting Systems (RWHS) for provided water for approved non-potable end
purposes of this document, are defined as uses.
systems that collect, store and use precipitation
collected from rooftops or other man made,
above ground collection surfaces. 1.2 ARCSA
The use of rainwater harvesting systems in The American Rainwater Catchment Systems
Georgia can serve to supplement non-potable Association (ARCSA) is one of the best
water demands while maintaining and sources of information about rainwater
harvesting. ARCSA (www.arcsa.org), an
enhancing the quality of the environment.
affiliate of the International Rainwater
These guidelines are intended to be consistent
with, and complimentary to, the requirements Catchment Systems Association (IRCSA,
of the Georgia’s 2009 Amendments to the 2006 www.ircsa.org ) is an organization formed in
International Plumbing Code, National Institute 1994 by Dr. Hari J. Krishna in Austin, Texas.
of Health, and local Boards of Health. ARCSA's primary mission is to promote
rainwater catchment systems in the Americas
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through educational opportunities, the
exchange of information at the ARCSA website
and regularly scheduled workshops and
courses.
ARCSA has published guidelines for rainwater
harvesting systems, and is currently writing
national standards for the rainwater harvesting
industry, both of which are available on their
website. Currently Rainwater Catchment
Design and Installation Standards are being
developed by a joint effort of ARCSA and the
American Society of Plumbing Engineers
(ASPE). The purpose of these standards is to
assist engineers, designers, plumbers, builders/
developers, local government, and end users in
successfully implementing rainwater catchment
systems. These standards will apply to new
rainwater catchment installations, as well as
alterations, additions, maintenance and repairs
to existing systems.
Rainwater harvesting systems can range from a
simple 55 gallon rain barrel to a complex
multimillion-gallon cistern with electronic
pumps and controls. It is important to evaluate
existing site conditions of the project to ensure
compliance with state and local requirements
during the planning phase.
To assist in understanding the terminology of
RWH, a glossary of commonly used terms is
provided at the end of this document.
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CHAPTER 2
INTRODUCTION TO
RAINWATER HARVESTING
2.1 The Big Picture
The Earth’s surface is 75 percent covered by The United States population more than tripled
water; only 3 percent of this water is suitable from 76 million people in 1900 to 281 million
for human consumption. Of that 3 percent most people in 2000. The population growth of 32.7
is either locked in polar caps or hidden beyond million people in the 1990s was the largest
the practical reach of commercial technologies. numerical increase of any decade in U.S.
Less than 1 percent of our water is found in history (Hobbs, Frank and Nicole Stoops, U.S. Census
lakes, rivers, and approachable underground
aquifers. In addition, all freshwater sources are
“The city of Tucson, Arizona, on
derived from either rainfall or snowmelt. This
water then makes its way into the ground, or it Tuesday became the first
flows into inland freshwater bodies or the municipality in the country to
ocean. Fresh water is a diminishing limited require developers of commercial
resource, and though we cannot increase the properties to harvest rainwater
Earth’s supply of water, we can manage what
for landscaping. The new water-
supplies we have more effectively.
saving measure - approved by a
Global consumption of water has been unanimous vote by the City
doubling every 20 years, more than twice the Council -- mandates that new
rate of human population growth. We are using developments meet 50 percent of
water as if it is an infinite resource, but it’s not.
their landscaping water
We are in fact depleting our planet’s usable
requirements by capturing
water supply. Shrinking fresh water supplies
present the most urgent and potentially rainwater. The new rule goes into
catastrophic environmental problem today effect June 1, 2010.” http://
worldwide (Barlow, 2002). www.biologicaldiversity.org/
news/center/articles/2008/land-
letter-10-16-2008.html.
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Figure 2.1 Statewide Water Level Restrictions
Bureau, Census 2000 Special Reports, Series CENSR-4, Excluding agriculture, one estimate for
Demographic Trends in the 20th Century, U.S.
Georgia’s average daily per-capita water
Government Printing Office, Washington, DC, 2002).
consumption is estimated at 168 gallons
Statewide (Georgia) public-supply water use compared with a national average of 153
has increased steadily since 1980, gallons. Steps need to be taken to ensure that
corresponding to an increase in population Georgia’s water supply continues to meet the
during the same period.” “Water use for public needs of the economy (Dodd, http://
supply likely will continue to increase as the www.gppf.org/article.asp?RT=20&p=pub/Water/
envwateruse040528.htm).
S t a t e ’s p o p u l a t i o n g r o w s . ” ( h t t p : / /
ga.water.usgs.gov/pubs/other/ggs-ic106/pdf/ggs- Rainwater harvesting systems address many
ic106.pdf). water issues associated with population growth
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and urban expansion,, such as reduced public and building new pipelines and associated
water consumption improved stormwater technologies (Texas Manual, 2006).
quality and increased soil infiltration.
We all use rainwater either directly or Rainwater harvesting can be envisioned as
indirectly. Water from a municipal source, an relieving, not replacing, some of the burden
example of an indirect use of rainwater, comes placed on the existing public utilities especially
from a spring or reservoir fed by rainfall and during times of drought and high demand.
snowmelt, the ultimate suppliers of these
sources. Because the water runs across parking 2.2 History
lots and highways, through fields that may The collection and use of rainwater is not new.
have been treated by pesticides, down storm Long before centralized water delivery and
gutters, and into the lakes and streams, the treatment systems were built, our ancestors
municipal water authority has to treat the water knew that access to water was a basic necessity
with chemicals to kill pathogens and correct for for survival. Archeological evidence of RWH
pH. Rainwater harvesting, an example of a techniques date back at least 4,000 years. Ruins
direct use of rainwater, is not exposed to the of cisterns have been found in Israel, believed
same pollutants and therefore does not require to be from 2,000 BC. The concept of rainwater
the same level of treatment as water which harvesting may date back 6,000 years (Gould
flows overland and underground before it’s and Nissen-Peterson 1999).
collected. Public utilities have the added
burden of maintaining existing supply and In the 20th century, large-scale public water
stormwater infrastructure as well as designing systems were developed in industrialized
During a Level 4 drought, virtually all outdoor water use is prohibited. A
Level 4 drought is an “extreme drought,” with lake levels, stream flows and
rainfall at or approaching the lowest levels in 100 years. In Georgia, a Level
4 drought was declared in 2007 for the northern third of the state,
including the metropolitan Atlanta area. The declaration was made because
rainfall in this portion of the state was more than 20 inches below normal
(see http://www.caes.uga.edu/topics/disasters/drought/
totalrainfallmap .html) in 2007 and 2008, and stream flows were far below
normal across the state.
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Figure 2.2 Lake Lanier Level Diagram
countries and RWH became restricted to IRCSA to promote and advance rainwater
specialized applications and regions, such as on catchment systems technology.
small islands and in semi-arid rural areas of the
world. Law in the U.S. Virgin Islands and
2.3 Current Usage of
many other Caribbean Islands requires RWH
due to limited fresh water sources. Interest in
Rainwater
RWH in the United States and around the globe There may be as many as 250,000 RWH
has grown significantly in recent years due to systems in use in the United States (Kincade,
d r o u g h t s a n d w a t e r s h o r t a g e s . RW H 2007). Texas, Virginia, Oregon, the state of
associations are forming in countries all over Washington, and other states have developed
the world and many are now joining together in guidelines for designing and installing
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rainwater harvesting systems. In Hawaii, up to now source their water from rainwater tanks.
60,000 people depend on RWH systems for Countries such as Germany, Australia, New
their water needs (Macomber, 2001). In India, Zealand, Great Britain, Sri Lanka, India,
since June 2001, the Ministry of Urban affairs Pakistan and others
and Poverty Alleviation has made rainwater are considerably farther along in their
harvesting mandatory in all new buildings with understanding and regulation of the use of
a roof area of more than 100 square meters and rainwater. In some instances both local and
in all plots with an area of more than 1,000 national authorities insist on designed and
square meters, that are being developed (http:// installed rainwater catchment systems
w w w. r a i n w a t e r h a r v e s t i n g . o r g / U r b a n / integrated into new developments.
Legislation.htm). In the United States some
municipalities require RWH systems in new 2.4 Response to Drought
developments. Tucson, Arizona recently passed By August 2000, 36 percent of the United
the nation’s first rainwater harvesting States was in severe to extreme drought,
ordinance for commercial properties. Currently leading to widespread wildfires and other
more than 10 percent of New Zealanders rely drought-related damages (Natl Oceanic and
on rainwater for their drinking needs (Abbott, A tmospheric Administration Climate of 2000 - September,
U.S. Drought National Climatic Data Center, 16 October
2008). In Australia 17 percent of households
Figure 2.3 Aerial Photo of Lake Lanier 2007
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2000 (National Oceanic and Atmospheric Administration, there will always be a supply of clean water in
.
2001; U.S. Department of Agriculture, 2000) Georgia and in our region as a whole. Recent
drought conditions in the Southeast and in
Georgia in particular have triggered many
According to David Stookesbury, state
municipalities and governing bodies to place
climatologist for the state of Georgia, the
water restrictions on the use of municipal water
period between WWII and the late 1970s was
( F i g u r e 2 . 1 , S t a t e w i d e Wa t e r L e v e l
an abnormally benign climatic period. Since
Restrictions). In some instances outdoor
the late 1970s we returned to a more normal
watering has been banned completely. Even
climate pattern that involves greater year-to-
more alarming is the possibility of
year variability in temperature and rainfall. For
implementing contingency plans for prioritized
city planners, public water authorities and the
use of municipal water supplies. RWH has
agriculture industry, this means increased
great potential for supplying water for various
difficulty in planning.
uses in the midst of these restrictions.
It has generally been taken for granted that
Figure 2.4 Basic Hydrological Cycle
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Figure 2.5 The Hydro-Illogical Cycle
The city of Atlanta derives most of its water boundary between Georgia and Tennessee has
from Lake Lanier. In December 2008, lake been recently disputed over water rights in the
levels were near the all time low (Figure 2.2, Tennessee River. The aerial view of drought-
Lake Lanier Level Diagram). As difficult as stricken Lake Lanier (Figure 2.3, Aerial Photo
this is to imagine, there is a finite amount of of Lake Lanier, 2007) makes it clear that
water in the lake. Once the water level goes actions must be taken to address water supplies
below the level of the intakes, there is no way in our State.
to extract any more water until the lake is
replenished by additional rains, or until the Water conservation is in the minds of many of
intake is lowered, which could require our citizens and policy makers. Unlike other
dredging and large capital outlays. natural disasters, drought does not have a
clearly defined beginning and end. As a result,
Water rights and water availability are our reaction to drought traditionally has not
important and relevant topics today. Politics, been timely. It is human nature to think that
industrial interests, and environmental just because it rained yesterday that the drought
concerns all play into this picture. The state is over. This is largely due to widespread lack
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of understanding of the basic hydrological • RWH is by nature decentralized and
cycle (Figure 2.4, Basic Hydrological Cycle relatively less vulnerable to natural
National Drought Mitigation Center, disasters than public water supplies.
University of Nebraska, Lincoln, Nebraska, • Harvested Rainwater is low in
USA). minerals and it is ideal for activities
such as car washing. Since it
Public attention tends to wane after significant contains no chlorine, rainwater is
rain events and sometimes after small ones. also ideal for filling garden ponds
The cartoon in Figure 2.5, The Hydro-Illogical and irrigating sensitive plants.
Cycle, cleverly illustrates the point that • Widespread adoption of rainwater
appearances can be deceiving. harvesting can increase the
efficiency of expensive water
2.5 Benefits supply infrastructure.
Given the variability in the amounts and timing
of rainfall received, collecting water when it
2.6 Economics and
comes in abundance for use at a later time is
logical and sustainable. Integrating rainwater
Feasibility
harvesting concepts into new construction Municipal water is generally purchased at
design generally does not present relatively low rates throughout the state.
overwhelming problems. Retrofitting most According to EPA region 4 Environmental
buildings to collect the rainwater that is Finance Center, the median monthly amount
ordinarily piped away is a relatively simple charged for minimum usage of water is $10.00,
procedure. In many cases, the gutters, $20.50 for 6,000 gallons, and $29.50 for
downspouts and pipes are already present on 10,000 gallons. As a point of comparison, a
the building. gallon of potable water at a major grocery
The numerous benefits and advantages in retailer is $1.20 per gallon while the median
harvesting rainwater include the following: bill for 6,000 gallons is $0.0034 per gallon
• Rainwater is free. Although its which is approximately 350 times cheaper
initial equipment installation costs (http://www.efc.unc.edu/publications/pdfs/
can be significant, long-term costs GA2007WaterSewerRatesReport.pdf).
are workable, given our
circumstances. For most Georgians, spending significant
• Stored rainwater gives its owner amounts of money on a RWH system is low on
more independence from the effects the priority list. When calculating the
of irregularities of rain events. “payback” for a residential or commercial rain
harvesting system, costing in the thousands of
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dollars, often the investment cannot be justified pressure on municipal and private water
based only on the relatively cheap cost of supplies. Understanding how to implement
municipal water. Perhaps it makes more sense these technologies is key in rainwater
to think in terms of the overall ecological harvesting as a viable safe supplement to a
benefit gained from reducing demands on shrinking water supply.
public fresh water supplies.
For some individuals the satisfaction of
catching the rain is motivation enough. Fresh
water demands from ground sources (wells),
both public and private can also be reduced by
using rainwater. It is worth pointing out that in
some instances, the only thing preventing the
loss of an established landscape during periods
of outdoor watering restrictions is a RWH
system. For some residents, having the peace
of mind that their new or existing landscape
will survive and thrive is the only motivation
needed to install a RWH system. In the case of
some businesses in some municipalities in the
Southeastern US, the ability to remain in
business has depended on a functioning RWH
system.
2.7 In conclusion
Worldwide freshwater shortages clearly
indicate that immediate action must be taken to
implement RWH technologies. Rainwater
Harvesting has been practiced since ancient
times. We know from history that local and
regional droughts occur on a regular basis
throughout the world. We also know that many
thousands of RWH systems exist throughout
the US and that when they are properly
designed and installed they are able to provide
many benefits, most immediately to alleviate
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CHAPTER 3
SYSTEM SIZING AND
WATER BALANCING
RWH systems can range from the very simple public commercial buildings, educational
to the very complex. It is absolutely facilities and homes. For example, the Energy
fundamental to determine the reasons for Policy Act of 1992 requires that from January
collecting rainwater prior to designing any 1994 onward all toilets sold in the United
system. There are many reasons for wanting to States use no more than 1.6 gallons of water
have a RWH system; however, three of the per flush, well below the 3.5 gallons per flush
most important reasons are: used by most American toilets (Energy Policy Act
of 1992. Public Law 102486, 102nd Congress.
• Wa t e r c o n s e r v a t i o n a n d
Washington, D.C. Oct. 24, 1992 http://www.cepis.ops-
supplemental water supply; oms.org/muwww/fulltext/repind48/energy/energy.html).
• Storm water reduction; and
• Achieving Green building goals. Georgia’s average daily per-capita water
consumption, excluding agriculture, is
Examining these three areas (water estimated at 168 gallons compared with a
conservation, stormwater runoff reduction, and national average of 153 gallons. Only one
Green building) helps focus on the benefits of percent of this water is used for drinking
collecting rainwater and establishes specific purposes (Benita Dodd, Georgia Public Policy
parameters in designing a rainwater system. If Foundation (May 28, 2004), http://www.gppf.org/
a project must be 20 percent more water default.asp?pt=news&RT=20). Even during times
efficient or must reduce site runoff by 60 of drought there is plenty of rainfall in Georgia
percent, a specific goal has been established for that can be harvested and used to supplement
assistance in determining the type and size of the demands for non-potable purposes such as
the rainwater system required to meet these landscape watering, toilet and urinal flushing,
project objectives. and cooling tower makeup.
Water used for non-potable purposes does not
3.1 Water Conservation require the same level of treatment as water
Conservation practices are those that help us that must meet EPA drinking water quality
extend the usefulness of a specific resource. standards. In order to safely serve these needs,
Water conservation makes good economic this water must have, however, appropriate
sense and is sometimes law for private and quality. See Chapter 5 for more information on
water quality.
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USE GALLONS PER % OF DAILY TOTAL
CAPITA
POTABLE INDOOR USES:
Showers 11.6 7%
Dishwashers 1 0.60%
Baths 1.2 0.80%
Faucets 10.9 6.60%
Other uses, leaks 11.1 6.70%
Subtotal potable indoor uses 35.8 21.70%
NON-POTABLE INDOOR USES:
Clothes washers(Non permissable per 15 9.10%
code in GA)
Toilets 18.5 11.20%
Subtotal non-potable indoor uses 33.5 20.30%
NON-POTABLE OUTDOOR USES 95.7 58%
Table 3.1 Percentage of water uses
3.2 Stormwater Runoff soak into the ground as close to the location
where it falls, is another goal of LID. A RWH
Reduction system can act as a large sponge, absorbing and
Low Impact Development (LID) is a design storing water for later use. The water can then
and site development methodology that allows be released at a slower rate via landscape
newly developed and/or existing sites to watering.
hydrologically mimic pre-development
conditions. For example, if a forested area is Stormwater retention requirements can be
developed for commercial purposes, one LID partially achieved by incorporating RWH as an
goal would be to mimic some of the integral part of the design (http://
hydrological functions of trees and encourage www.lowimpactdevelopment.org/). From 1991 to
cleansing and infiltration of site rainwater 2005 the state of Georgia has had an increase
runoff. Capturing rain and encouraging it to of 111% in the amount of impervious surface,
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increasing its impervious area from 216,805 3.3 Green Building
acres to 455,337 acres (Natural Resources Spatial With the growing awareness of the need to
Analysis Laboratory, College of Agricultural and
reduce our footprint on the environment, a new
Environmental Sciences, UGA http://narsal.uga.edu/
movement toward a more conscious,
glut/ecoregion.php?ecoregion=5). In urban areas
sustainable and wise development has been
across the state, rain
dubbed “Green.”
falls on a roof surface,
Many building
travels through a gutter/ The National Green Building
organizations have
piping network, and Standard offers the following points programs with
eventually arrives as
for rainwater collection: rating systems for
stormwater into a creek
new developments,
or river. Impervious 801.11 Rainwater collection and
homes and
surfaces force water to
distribution. commercial
flow rapidly through
buildings. These
stormwater systems and (1)Rainwater is collected and
rating systems are
thus overwhelm creek used: 6 points based in
and stream banks,
sustainability
causing ongoing (2)Rainwater is distributed using a
s t a n d a r d s .
ecological degradation. renewable energy source or
R a i n w a t e r
gravity: 2 points harvesting can
Unfortunately in some
assist in achieving
urban environments in Courtesy of NAHB 2009
the desired level of
Georgia, sewage and
(National Association of Home "Green." For
stormwater still flow in
example, the
the same pipe networks. Builders)
N a t i o n a l
During particularly w w w. n a h b r c . o r g / t e c h n i c a l / s t a n d a r d s / Association of
heavy rain events, raw gbversion1_chapter08.pdf
Home Builders
untreated sewage may
(NAHB) has a
be carried directly into
program that
creeks and streams.
awards points for integrating a RWH system
Harvesting some of the rainwater before it
into the construction of new homes. NAHB,
enters the stormwater drainage system can help
the International Code Council (ICC) and the
reduce peak flow volumes during these rain
NAHB Research Center have initiated a
events and therefore lessen the environmental
process for the development of an ANSI
impacts of these combined systems.
standard for Green home building construction
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Harvested Water (gal) =
catchment area (sq.ft.) X depth (in.) X 0.623
(conversion factor)
A simple estimate of the number of gallons that can be harvested from a given
catchment area after a rainfall event can be determined with the following
formula. The total number of
gallons harvested is equal to the catchment area (square feet) times the depth
of a rainfall (inches) times a conversion factor of 0.623.
practices, which is titled The National Green for a total of 41 consecutive dry days, a record
Building Standard™ ( http://www.nahbrc.org/ in the state (http://www.ncdc.noaa.gov/oa/climate/
technical/standards/gbinvitation.aspx). extremes/2000/october/octoberext2000.html).
Selecting materials for rainwater systems based
on locally available components and equipment Rainfall is fairly evenly distributed throughout
containing recycled content may achieve the year in the state of Georgia. This even
further credit. distribution enables storage capacity to be
somewhat less than in other areas of the
3.4 System Sizing country (arid southwestern states) where
rainfall occurs more seasonally (longer periods
A basic goal for sizing any rainwater
of time between rain events). Storage capacity
harvesting system is to balance the volume of
needs to be sufficient to store water collected
water that can be captured and stored (supply),
during heavy rain events to last through dry
compared to the volume of water used
periods. Some residences might be constrained
(demand). In order to “balance” the system, the
by the size of the collection surfaces and/or the
supply must equal or exceed the demand. This
volume of storage capacity that can be installed
is easiest to understand if broken down on a
due to space or costs. The following sections
monthly basis.
describe ways to determine the amount of
rainfall, the estimated demand, and how much
In Georgia, the longest anticipated period
storage capacity is needed to provide enough
between rain events is normally less than 30
rainwater to meet the demand. The rainfall data
days. However, no measurable rain fell from
for selected Georgia cities is found in Table
September 25th through November 4th, 2000
3.2, Major Georgia Cities Annual Precipitation.
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Note: It is important to
understand that regardless of
the pitch, the shape, or the
complexity of any roof
surface, it is the overall
footprint of the building that
determines the collection
area. (see Figure 3.1)
Figure 3.1 Catchment area of typical roofs
3.5 How Much Water Can
Be Captured? surface is the area covered by collection
surface (length times width of the roof from
Approximately 0.62 gallons per square foot of eave to eave and front to rear). Obviously, if
collection surface per inch of rainfall can be only one side of the structure is guttered, only
collected during a rain event. Some rainwater the area drained by the gutters is used in the
is lost to first flush (see components, see calculation. For commercial buildings refer to
glossary), evaporation, splash-out or overshoot the plumbing code for additional sizing
from the gutters in hard rains, and possible requirements.
leaks. Rough collection surfaces are less
efficient at conveying water, as some of the •Rainfall Distribution
water captured on porous surfaces tends to be
According to the Georgia State Climatology
lost to evaporation. A much more in depth
Office, average annual rainfall in Georgia
analysis of how to calculate potential harvested
varies from a low of about 40 inches in
rainwater is available through the ARCSA
Montgomery County to a high of over 80
website (http://www.arcsa.org/resources.html)
inches in isolated mountainous areas in the
in their guidelines publication.
northeastern part of the state. If the rainwater
harvesting system is intended to be the sole
•Collection Surface water source for a specific use, the catchment
The collection surface is the “footprint” of the area and storage capacity must be sized to meet
roof. In other words, regardless of the pitch or the water demand through the longest expected
shape of the roof, the effective collection
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City JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL
ATLANTA 5.03 4.68 5.38 3.62 3.95 3.63 5.12 3.67 4.09 3.11 4.10 3.82 50.20
ATHENS 4.69 4.39 4.99 3.35 3.86 3.94 4.41 3.78 3.53 3.47 3.71 3.71 47.83
MACON 5.00 4.55 4.90 3.14 2.98 3.54 4.32 3.79 3.26 2.37 3.22 3.93 45.00
COLUMBUS 4.78 4.48 5.75 3.84 3.62 3.51 5.04 3.78 3.07 2.33 3.97 4.40 48.57
SAVANNAH 3.95 2.92 3.64 3.32 3.61 5.49 6.04 7.20 5.08 3.12 2.40 2.81 49.58
AUGUSTA 4.95 4.11 4.61 2.94 3.07 4.09 4.07 4.48 3.59 3.20 2.68 3.14 44.58
VALDOSTA 5.79 4.47 5.30 3.61 3.15 4.91 6.30 5.24 4.11 3.11 3.24 3.83 53.06
Table 3.2 Major GA Cities Annual Precipitation 1971-2000 - 30 year average (inches)
NOAA – National Weather Service Forecast Office, www.srh.noaa.gov Weather Channel, www.weather.com
interval without rain. If additional water is precipitation ranges from 3.4 inches in
required, other water sources must be November to 5.3 inches in July. The monthly
considered to supplement the collected distribution of rainfall is an important factor to
rainwater. consider for sizing a system.
Some rainfall collected from high-intensity, • Monthly Rainfall Estimation
short-duration rain events, may be lost to Rainfall estimates should always be prepared
overflow from storage tanks or splash out from for a specific locale, using the best data that
the gutters. Since these intense rainfall events apply to that area. Two different estimators of
are considered part of the cumulative annual monthly rainfall are commonly used: average
rainfall, the total available volume of such an rainfall and median rainfall. Taking the sum of
event is rarely captured. historical rainfall and dividing by the number
Another consideration is that annual rainfall is of years of recorded data calculates average
not evenly distributed throughout the twelve annual rainfall. Information on rainfall data is
months of the year. Statewide average monthly available from numerous public sources,
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Rainfall Area X Gallons/Sq.
Total Gallons
(in.) (Sq. Ft.) Ft.
1 2,200 0.62 1,364.00
5 2,200 0.62 6,820.00
10 2,200 0.62 13,640.00
40 2,200 0.62 54,560.00
50 2,200 0.62 68,200.00
1 3,500 0.62 2,170.00
5 3,500 0.62 10,850.00
10 3,500 0.62 21,700.00
40 3,500 0.62 86,800.00
50 3,500 0.62 108,500.00
1 5,000 0.62 3,100.00
5 5,000 0.62 15,500.00
10 5,000 0.62 31,000.00
40 5,000 0.62 124,000.00
50 5,000 0.62 155,000.00
Table 3.3 Table for rainwater potential collection from roof surfaces
including the National Climate Data Center 3.6 Calculating Storage
website (NOAA, Climatography of the United
States No. 85, Section 2: Precipitation.NCDC:
Capacity
* National Climatic Data Center (NCDC).* Once the potential for rainfall capture volume
Median rainfall is the amount of rainfall that is known from rainfall data and catchment
occurs in the midpoint of all historic rainfall area, the next step is to calculate storage
totals for any given month. In other words, capacity. The decision of whether rainwater
historically for the month in question, half of will be used for irrigation, non-potable
the time the rainfall was less than the median domestic use, or both, will factor into how
and half of the time rainfall was more than the much water will be used, thus dictating water
median. demand.
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American Water Works (AWWA) Research
If a rainwater harvesting system is to be the Foundation. Of this amount, 42 percent is used
sole water supply for a set of specific uses, indoors, and the remaining 58 percent is used
overbuilding ensures a safety margin. If budget outdoors. By far the largest percentage of
constraints do not allow the user to install as indoor water use occurs in the bathroom for
much storage capacity as a sizing method toilet flushing (18.5 gal/person/day) and
indicates, it is important to provide an area showering (11.6 gal/person/day). Clothes
where additional tanks or cisterns can be washers were the second largest water users
installed at a later date when finances permit (15 gal/person/day).
(Texas Manual, 2006). A simple method for most residences of
estimating outdoor irrigation demand is
•Monthly Demand and Supply analyzing the water bill and comparing water
One method of determining the feasibility of a usage between the summer and winter months.
proposed system is the monthly water balance If water is used for landscape and gardening,
method. This method of calculation is similar there will typically be a spike in volume used.
to maintaining a monthly checkbook balance. The difference between the summer and winter
Starting with an assumed volume of water months will typically be the monthly outdoor
already in the tanks, the volume captured each usage. It is shocking to many people when they
month is added to the previous balance and the discover the vast volume of water that is used
monthly demand is subtracted. The initial to water lawns.
volume of water in the tanks would be
provided by hauling or capturing water prior to •Estimating Indoor Water Demand
withdrawing water from the system. Data and Currently the only approved application of
calculations can be entered on an electronic rainwater in Georgia for indoor purposes are
spreadsheet to enable the user to compare toilet and urinal flushing and cooling tower
different variables of catchment area and make-up. Although a number of states have
storage. It is suggested that perspective system approved rainwater for use in automatic clothes
owners experiment with different variables of washers (washing machines), this is not
storage capacity and, if applicable, catchment permissible in Georgia.
surface to find the desired level of comfort and
affordability for catchment size and storage Most American families flush the toilet an
capacity. average of 4 times per day per person.
Calculating 1.6 gallons per flush, a family of
•Estimating Demand four will use approximately 25.6 gallons per
North American households use approximately day or a total of 768 gallons per month. If toilet
146,000 gal of water annually, according to the flushing will be the sole usage of rainwater for
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a household, then planning for 30 days with
minimal or no rain, would require a storage
tank of at least 768 gallons, or the next closest
size (AWWA http://www.cepis.ops-oms.org/muwww/
fulltext/repind48/energy/energy.html).
3.7 Water Conservation
Supplemental to Other
Resources
It is impossible to separate water conservation
from system sizing, because the water demand
determines the system size. Consciously
conserving water (water-conserving plumbing
fixtures, shorter showers, less outdoor
irrigation, etc.) decreases the total demand.
This results in more efficient use of our
resources and enables us to do more with what
we already have. For information on residential
water efficiency, visit the Water Saver Home
w e b s i t e ( w w w. h 2 o u s e . o rg ) , a v i r t u a l
encyclopedia of water-saving tips, and
AWWA’s drinktap.org consumer website.
3.8 Summary
Rainfall events are complicated and an indepth
understanding of local rainfall is imperative.
Those comtemplating designing or installing a
RWH system should have an adequate amount
of rainfall data, in order to properly size their
system (ARCSA GUIDE 2009, Chapter 8).
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CHAPTER 4
HARVESTING
COMPONENTS
4.1 Introduction and
Fundamental Elements
Rainwater harvesting is the capture, diversion, installing a RWH (See figure 4-3, Rainwater
and storage of rainwater for a number of Harvesting Flow Chart).
different purposes including landscape
irrigation, non-potable domestic use, aquifer Rainwater systems are available in many
recharge, and storm water abatement. configurations. Some have below ground
Understanding how the fundamental storage tanks, above ground tanks, indoor
components of a rainwater system work is controls, and some have outdoor controls.
crucial when contemplating designing or Figures 4.1 and 4.2 illustrate the primary
Figure 4.1 Diagram of above ground cistern
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Figure 4.2 Diagram of below ground cistern
components of each type. If the end use is
indoors for toilet and urinal flushing, or for • Gutters and downspouts: conduits that
cooling tower make-up, treatment components channel water from the roof to the tank.
are included as well. • Downspout filtration, leaf screens, first-flush
diverters, and roof washers: components that
Many factors influence component selection remove debris and dust from the captured
when designing or selecting the right rainwater rainwater before it goes to the tank.
system for a specific end use application. • Storage: one or more storage tanks, also
Gutters, downspouts, buried utilities, soil types, called cisterns.
soil depths, slopes, site drainage, existing • Pumps and controls: devices such as level
plumbing, electricity, diversion of overflows, indicators, makeup water supplies, back flow
local restrictions, neighborhood covenants, and preventers and or air gaps.
neighbors are some of the many items that • Treatment and disinfection: for non-potable
deserve attention when siting RWH systems. indoor systems, filters and other methods to
Regardless of the complexity of the system, make the water suitable for use in toilet
rainwater harvesting systems are comprised of flushing, urinal flushing and as cooling tower
six basic elements: make-up.
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RAINWATER HARVESTING FLOW CHART
Catchment Surface
First flush
Inlet Filtration
Calming Inlet
Back flow
Prevention Storage
Make up supply Vector Overflow
Municipal or well Prevention
Air Gap
Distribution
Pumps, controls, etc
Filtration
Indoor Use Outdoor Use
Disinfection Sediment
Evaporative Toilets and Outdoor
Cooling Urinals Irrigation,
Hose bib
Figure 4.3 Rainwater Harvesting Flow Chart
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4.2 The Catchment
Surface
The roof of a building or house for purposes of Condensate
this document is the only choice for the While technically not originating
catchment surface. Water quality from different from a roof surface, condensate
roof catchment surfaces is a function of the
from air-conditioning
type of roof material, climatic conditions, and
the surrounding environment (Vasudevan, (dehumidification) units
2002). Common sense should prevail in collectively represents a
deciding whether or not to collect water from a
significant source of water in both
particular surface. Care should be taken in
considering how certain roofing materials that residential and commercial
come in direct contact with rainwater affect its applications. The amount of water
quality. Once again, the end use will ultimately that can be collected from any
determine the viability of a given surface. The
given indoor environment varies
major roof surface types commonly found in
Georgia are listed below. greatly, depending on seasonal
climatic conditions, HVAC
-Metal Roof equipment and building size. Five
The surface texture affects the quantity of to twenty-five gallons per day can
rainwater that can be collected from a given
be collected from many single
roof, the smoother the better (Texas Manual,
2006). Powder coated steel is one of the best family residences. Significantly
surfaces to consider. It is very smooth and larger volumes can be collected in
water sheds off it easily during rain events. In commercial applications. This
addition, it resists corrosion for extended
condensate water can be routed
periods of time. Although relatively more
expensive than other roof materials, metal either by gravity flow, or with the
roofs will outperform most other types over aid of a condensate sump pump
time.
directly to the rainwater storage
tank.
-Clay/Concrete and Tile Roof
Clay and concrete tiles are both porous. These
materials contribute to as much as a 10 percent
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loss due to texture, inefficient flow, or -Slate
evaporation. To reduce water loss, tiles can be Slate’s smoothness makes it ideal for a
painted or coated with a sealant. There is some catchment surface. However, cost
chance of toxins leaching from the tile sealant consideration may preclude its use.
or paint, but this roof surface is safer when
coated with a special sealant or paint to prevent
-Vinyl/rubberized
bacterial growth on porous materials. The
There are many new roofing materials on the
potential for chemical leaching should be
market today primarily used in commercial
considered if the water will be used for
construction. These materials typically have
livestock, fish ponds, or other end uses with
thermally or chemically welded seams. Check
special water quality considerations (Texas
with the roofing material manufacturer for
Manual, 2006).
suitability as a collection surface.
-Composite or Asphalt Shingle
The vast majority of residential roof surfaces in
4.3 Gutters and
the United States are made of composite Downspouts
asphalt shingles. For applications discussed in
Rood gutters direct the flow of rainwater
this guide, i.e., non-potable indoor use and
running off the eaves of a building. Some
outdoor irrigation, there is little evidence to
suggest serious detrimental water quality gutter installers can provide continuous or
impacts resulting from rainwater from this type seamless gutters. The most common materials
for gutters and downspouts are half-round
of surface. Cistern water should be protected
PVC, vinyl, and seamless aluminum.
from asphalt shingle grit granules and be
Regardless of material, other necessary
screened by a fine downspout filter.
components in addition to the horizontal
gutters are the drop outlet, which routes water
-Wood Shingle, Tar, and Gravel
from the gutters downward through the
These roofing materials are increasingly rare in
downspout pipe. Whenever possible, fit the
new construction, and the water harvested from
downspout pipe snugly to the side of the house.
this type of surfaces can contain certain
If this is not possible then simply make sure
contaminants that may limit its use, due to
that the pipe is stable and is firmly connected
leaching of some chemical compounds (Texas
to the inlet of the tank using rubber grummets.
Manual, 2006).
Avoid downspouts/pipes installations that
could be easily knocked out of position. Sound
building and construction practices should
prevail. Additional components include the
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concentrates rainfall runoff from two roof
planes before the collected rain reaches a
A calming inlet is designed to gutter. Depending on the size of roof area
mix the relativelly more
terminating in a roof valley, the slope of the
anaerobic water at the bottom of
the tank with the more roof, and the intensity of rainfall, the portion of
oxygenated water closer to the gutter located where the valley water leaves the
surface of the tank. This is eave of the roof may not be able to capture all
installed at the end of the inlet the water at that point. This can result in
pipe and rests on the bottom of
excessive spillage or overrunning. Therefore
the tank.
consider installing an overrun dam to minimize
water lost at these valley points during heavy
rain events (Texas Manual, 2006).
Other factors that may result in over running of
gutters include an inadequate number of
downspouts, excessively long roof distances
from ridge to eave, step roof slopes, and
inadequate gutter maintenance. Variables such
as these make any gutter sizing rule-of-thumb
difficult to apply. Consult your gutter supplier/
Figure 4.4 Calming Inlet installer about your situation with special
attention to determine where excessive splash-
hardware, brackets, and straps to fasten the out may occur (Texas Manual, 2006).
gutters and downspout to the fascia and the
wall, and finally to the storage tank itself. Gutters should be installed with a slope
(Texas Manual, 2006). towards the downspout. Common sense
building should prevail whenever modifying or
installing a new roof gutter system.
-Gutter Sizing and Installation
Always check with the local building authority
as to compliance with local codes and 4.4 Primary Filtration
ordinances. It is important to consider that
To remove debris that gathers on the catchment
many roofs consist of one or more roof
surface, and assure high quality water, some
“valleys”. A roof valley occurs where two roof
filtration is necessary. Some of the many types
planes meet. This is most common and easy to
of filters are shown below.
visualize when considering a house with an
“L” or “T” configuration. A roof valley
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-Downspout Filters
The funnel-type downspout filter is typically
made of PVC and fitted with an aluminum or
stainless steel screen (see Figure 4.5). This type
of filter offers the advantage of easy
accessibility for cleaning. The funnel is cut into
the downspout pipe at the same height or
slightly higher than the highest water level in
the storage tank. Care must be taken to have
the filter high enough to prevent contamination
from dogs, but low enough not to discourage
the owner/operator from maintaining and
cleaning the filter on a regular basis.
Figure 4.5 Downspout filter
-Strainer Baskets
-Leaf Screens Strainer baskets are spherical cage-like strainer
The best first defense in keeping debris out of a that fit into the inlet of the tank. The
rainwater harvesting system is a leaf screen homeowner may need to experiment with
along the gutter or in the downspout. It helps various strainer basket screen sizes. Available
prevent large debris form entering the storage screen sizes range from fine filters to coarse
tank. These screens are usually made of 1/4 mesh sizes. See Figure 4.6.
inch mesh in wire frames that fit along the
length of the gutter. Leaf screens must be
regularly cleaned to be effective. If not
regularly maintained, leaf screens can become
clogged and prevent rainwater from the
flowing into the tank. Built-up debris can also
harbor bacteria and compromise the quality of
water.
Leaf guards/screens are necessary in locations
where trees are nearby or overhanging (mpst
locations in the Southeastern U.S.). Guards
with profiles conducive to allowing leaf litter
to slide off are also available. Figure 4.6 Strainer Basket
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-First-Flush Diverters
Common sense tells us that a roof can be a
An exact one size fit-all formula for
natural collection surface for dust, leaves,
calculating how much initial water
blooms, twigs, insect bodies, droppings,
needs to be diverted from the tank
pesticides, and other airborne residues. The
as first flush does not exist
first-flush diverter routes the first flow of water
because there are so many
from the catchment surface away from the
variables. For example, the slope
storage tank. The flushed water can be routed
and smoothness of the collection
to a planted area. While leaf screens remove
surface, the intensity of the rain
the larger debris, such as leaves, twigs, and
event, the length of time between
blooms that fall on the roof, the first-flush
events (which adds to the amount
diverter gives the system a chance to rid itself
of acculmulated contaminants),
of the smaller contaminants, such as dust,
and the nature of the
pollen, and bird and rodent droppings.
contaminants. In order to
effectively wash a collection
The simplest first-flush diverter is constructed
surface and thus reduce the
with a PVC standpipe. The standpipe fills with
amount of contaminants entering
water first during a rainfall event; the balance
the collection storage, one must
of water is routed to the tank. The standpipe is
take into account the factors
drained continuously via a pinhole or bay
previously mentioned.
leaving the screw closure slightly open. In any
case, cleaning of the standpipe is accomplished
by removing the PVC cover and removing
collected debris after each rainfall event (Texas
Manual, 2006). There are several other types of
first-flush diverters. The ball valve type
consists of a floating ball that seals off the top
of the diverter pipe (Figure 4.7) when the pipe
fills with water. Opinions vary on the volume
of rainwater to divert to the first flush device.
The number of dry days, amount and type of
debris, and roof surface are all variables to
consider.
Figure 4.7 First Flush Diverter
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Georgia Rainwater Harvesting Guidelines
4.5 Storage Ferrocement owner-built tanks are another
option and can provide significant storage at
The storage tank or cistern generally is the relatively low costs. Table 4.1 describes some
most important design of a component of a of these options and provides a feature
rainwater harvesting system. In most cases it is comparison.
permanent and its placement should be
carefully thought out. For purposes of practicality, this manual will
focus on the most common, easily installed,
The size of the storage is dictated by several and readily available storage options in
variables including: the rainwater supply (local Georgia. Storage tanks for indoor non-potable
precipitation), demand, projected length of use must be made of nonabsorbent and
time without rain (dry spells), catchment corrosion-resistant materials. Tanks must be
surface area (larger area equals more water), opaque, either upon purchase or painted later to
aesthetics, personal preference, and budget. A inhibit algal growth. Small
myriad of variations on amounts of light, especially
storage tanks and cisterns sunlight, can stimulate algal
Water weighs just over 8
have been used over the growth and can cause a thick
pounds per gallon, so
centuries, some of which soup-like formation in the
even a relatively small
are: earthenware cisterns in tank. In addition, rainwater
1,500 gallon tank will
ancient times, large pottery harvesting system storage
weigh 12,400 pounds.
containers in Africa, above- tanks must never have been
ground vinyl-lined used to store toxic materials.
swimming pools in Hawaii, Tanks must be covered and
concrete or brick cisterns in the central United provided with vents screened to discouraged
States, and galvanized steel tanks and attractive mosquito breeding. They must be accessible
site-built stone-and-mortar cisterns (Texas for cleaning and maintenance.
Manual, 2006).
-Tank Siting
An above-ground storage tank need not to be
Cisterns may be installed above or below
an eyesore. Plastic or metal tanks can be grade. In some project application tanks may
wrapped with wood and fitted with metal tops be partially buried or rainwater may be
resulting in aesthetically pleasing additions to collected in a small tank below ground and
the landscape. They can be screened with plant then pumped into an above ground storage
material or fencing. Corrugated metal tanks can
tank. Research local ordinances, covenants,
reflect architectural elements in some and restrictions, when selecting storage tank
commercial and residential applications. types. Determine if the tank will need to be
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30 Wednesday, April 1, 2009 DRAFT COPY GEORGIA RAINWATER GUIDELINES MANUAL
Georgia Rainwater Harvesting Guidelines
Figure 4.8 Wooden tank
buried or camouflaged. Consider how your The following are additional considerations
RWH system will be viewed by neighbors, and when selecting an ideal tank location. Locate
try to minimize any negative aesthetic impacts. tanks as close to the supply and demand points
as possible to reduce the distance water is
Underground utilities, high water tables or conveyed. To ease the load on the pump, tanks
shallow bedrock may limit the sites available should be placed as high as practicable. Of
for tank burial. Locate utilities, and investigate course, the tank inlet must be lower than the
groundwater and geological restrictions during lowest downspout from the catchment area.
the planning phase. Buoyant forces can act on When converting from the well water, or if
an empty underground and cause it to float out using a well backup, siting the tanks near the
of ground. Careful consideration should be well house facilitates the use of existing
given to manufacturer’s installation guides and plumbing. Overflow from tanks must be
instructions in order to correctly site and diverted to normal stormwater pathways in a
protect tanks against negative impacts of soils non erosive manner. In addition, water runoff
with a high water table. from tank overflow should not enter septic
system drain fields, and tank overflow and
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